fix(core): Fix index forwarding in the JSON decoding
fix(core): Fix index forwarding in the JSON decoding

Parsing an empty ExtensionObject did not increase the index.

open62541/open62541,open62541/open62541,open62541/open62541,JGrothoff/open62541,open62541/open62541,JGrothoff/open62541,jpfr/open62541,JGrothoff/open62541,jpfr/open62541,jpfr/open62541,JGrothoff/open62541,jpfr/open62541